[Libguestfs] [nbdkit PATCH 2/2] server/sockets: get rid of AI_ADDRCONFIG
Laszlo Ersek
lersek at redhat.com
Tue Jan 18 13:48:33 UTC 2022
The AI_ADDRCONFIG hint of getaddrinfo() is supposed to restrict the name
resolution to such address families (IPv4 vs. IPv6) for which the
resolving host has publicly routable addresses assigned.
The main problem with AI_ADDRCONFIG can be shown with the following
command line:
$ nbdkit -f -p 32776 -P pidfile -i ::1 -exit-with-parent null
On a host where ::1 is the only IPv6 address assigned (namely to the
loopback interface), the command fails with
> nbdkit: getaddrinfo: ::1: 32776: Address family for hostname not
> supported
due to the "publicly routable" requirement.
Remove AI_ADDRCONFIG from the getaddrinfo() hints, and as a replacement,
introduce the "-4" and "-6" options, similarly to netcat and ssh.
(1) This makes options of the form:
-i 127.0.0.1
-i ::1
work regardless of "public" IPv6 / IPv4 connectivity;
(2) options of the form
-i localhost
-i FQDN
will bind both IPv4 and IPv6 addresses of the desired interface(s);
(3) omitting the option "-i" will bind both IPv4 and IPv6 wildcard
addresses (0.0.0.0 and ::);
(4) the configurations in (2) and (3) can be restricted to IPv4 or IPv6
addresses by adding the "-4" or "-6" option, respectively.
Importantly, this change allows the "connect-tcp6" test case of libnbd to
pass on such hosts that have no IPv6 connectivity (i.e., where the only
assigned IPv6 address is ::1, namely on the loopback interface).
Ref: https://listman.redhat.com/archives/libguestfs/2022-January/msg00110.html
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
---
docs/synopsis.txt | 3 ++-
common/utils/windows-compat.h | 7 -------
server/internal.h | 1 +
server/options.h | 4 +++-
server/main.c | 9 +++++++++
server/sockets.c | 3 ++-
docs/nbdkit.pod | 20 +++++++++++++++++++-
7 files changed, 36 insertions(+), 11 deletions(-)
diff --git a/docs/synopsis.txt b/docs/synopsis.txt
index 07b9dcffe4f9..6154bb2e8805 100644
--- a/docs/synopsis.txt
+++ b/docs/synopsis.txt
@@ -1,4 +1,5 @@
-nbdkit [-D|--debug PLUGIN|FILTER|nbdkit.FLAG=N]
+nbdkit [-4|--ipv4-only] [-6|--ipv6-only]
+ [-D|--debug PLUGIN|FILTER|nbdkit.FLAG=N]
[-e|--exportname EXPORTNAME] [--exit-with-parent]
[--filter FILTER ...] [-f|--foreground]
[-g|--group GROUP] [-i|--ipaddr IPADDR]
diff --git a/common/utils/windows-compat.h b/common/utils/windows-compat.h
index 7695bf7ef7fb..658c1d8bc32b 100644
--- a/common/utils/windows-compat.h
+++ b/common/utils/windows-compat.h
@@ -75,13 +75,6 @@ struct sockaddr_un
#define O_NOCTTY 0
#endif
-/* AI_ADDRCONFIG is not available on Windows. It enables a rather
- * obscure feature of getaddrinfo to do with IPv6.
- */
-#ifndef AI_ADDRCONFIG
-#define AI_ADDRCONFIG 0
-#endif
-
/* Windows <errno.h> lacks certain errnos, so replace them here as
* best we can.
*/
diff --git a/server/internal.h b/server/internal.h
index 9e81eee629f6..f4843164025c 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -113,6 +113,7 @@ enum log_to {
LOG_TO_NULL, /* --log=null forced on the command line */
};
+extern int tcpip_sock_af;
extern struct debug_flag *debug_flags;
extern const char *export_name;
extern bool foreground;
diff --git a/server/options.h b/server/options.h
index e59ef17f90a1..39299b9d0173 100644
--- a/server/options.h
+++ b/server/options.h
@@ -59,8 +59,10 @@ enum {
VSOCK_OPTION,
};
-static const char *short_options = "D:e:fg:i:nop:P:rst:u:U:vV";
+static const char *short_options = "46D:e:fg:i:nop:P:rst:u:U:vV";
static const struct option long_options[] = {
+ { "ipv4-only", no_argument, NULL, '4' },
+ { "ipv6-only", no_argument, NULL, '6' },
{ "debug", required_argument, NULL, 'D' },
{ "dump-config", no_argument, NULL, DUMP_CONFIG_OPTION },
{ "dump-plugin", no_argument, NULL, DUMP_PLUGIN_OPTION },
diff --git a/server/main.c b/server/main.c
index 225258de710a..8e7ac149177d 100644
--- a/server/main.c
+++ b/server/main.c
@@ -86,6 +86,7 @@ static void error_if_stdio_closed (void);
static void switch_stdio (void);
static void winsock_init (void);
+int tcpip_sock_af = AF_UNSPEC; /* -4, -6 */
struct debug_flag *debug_flags; /* -D */
bool exit_with_parent; /* --exit-with-parent */
const char *export_name; /* -e */
@@ -367,6 +368,14 @@ main (int argc, char *argv[])
exit (EXIT_FAILURE);
#endif
+ case '4':
+ tcpip_sock_af = AF_INET;
+ break;
+
+ case '6':
+ tcpip_sock_af = AF_INET6;
+ break;
+
case 'D':
add_debug_flag (optarg);
break;
diff --git a/server/sockets.c b/server/sockets.c
index 45b6b1c49110..9b980a887f34 100644
--- a/server/sockets.c
+++ b/server/sockets.c
@@ -179,7 +179,8 @@ bind_tcpip_socket (sockets *socks)
port = "10809";
memset (&hints, 0, sizeof hints);
- hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
+ hints.ai_flags = AI_PASSIVE;
+ hints.ai_family = tcpip_sock_af;
hints.ai_socktype = SOCK_STREAM;
err = getaddrinfo (ipaddr, port, &hints, &ai);
diff --git a/docs/nbdkit.pod b/docs/nbdkit.pod
index 45a79528e2c9..009e96c8a823 100644
--- a/docs/nbdkit.pod
+++ b/docs/nbdkit.pod
@@ -173,6 +173,24 @@ Display information about nbdkit or a specific plugin:
Display brief command line usage information and exit.
+=item B<-4>
+
+=item B<--ipv4-only>
+
+=item B<-6>
+
+=item B<--ipv6-only>
+
+When a non-numeric argument is passed to the I<-i> option (such as a
+Fully Qualified Domain Name, or a host name from C</etc/hosts>),
+restrict the name resolution to IPv4 or IPv6 addresses.
+
+When the I<-i> option is omitted, listen on only the IPv4 or IPv6
+address of all interfaces (C<0.0.0.0> or C<::>, respectively).
+
+When both I<-4> and I<-6> options are present on the command line, the
+last one takes effect.
+
=item B<-D> PLUGIN.FLAG=N
=item B<-D> FILTER.FLAG=N
@@ -265,7 +283,7 @@ See also I<-u>.
=item B<--ipaddr> IPADDR
Listen on the specified interface. The default is to listen on all
-interfaces. See also I<-p>.
+interfaces. See also I<-4>, I<-6>, and I<-p>.
=item B<--log=stderr>
--
2.19.1.3.g30247aa5d201
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